Signal system



Feb. 10, 1931.

W. A. TOLSON SIGNAL SYSTEM Filed March 17, 1928 MOOl/L4 70R TRANS/Ml TTE/F Inventor X/LI i Lam A.Tolson. WM His Attorney.

, Patented Feb; 1 I 1931 wiLLrAM A. TOLSON, or REXFORD, NEW YORK, ASSIGNOR 'ro GnivnRAL-ELEc rnrocoMg PANY, A oonronerioiv or ew YORK SIGNAL SYSTEM Application filed March 17,1928. Serial no. 262,581.

' cillat-ion generators which are controlled'autom'aticallyin-response to application of signal'curr'ents to the transmitting apparatus. Means for efiecting this automatic control are shown and described in Patent No. 1,696,566 Eoof Emmett E Carter, issued December 25,

1928 'entitled High frequency duplex signaling" system whichis assignedto thesame assignee as thepresent application. It is likewise customarlyin systems of this kind to pro- Vida-means. for protecting the "receiving equipment against potentials which are induced in it during-periods whenthe transmitting equipment is' operating. Improved means for this purpose in'which an eleco tron'discharge device connected in shunt with the receiving circuit is controlled by the anodecurrent flowing in an automatically controlled oscillation generator are disclosed .in- Patent No. 1,696,593, Emmett F. Carter, issued December 25, 1928, entitled High frequency signaling system which is v alsoassigned to the same assignee as'the-present application.

In certain t es of si nals stems such for exampleyas in carrier current repeating systemsyit has'been found that the protection which isappliedito one'channel in response to application of signal currentsto' the other channel-should be very complete; In these systems an automatically controlled oscillation generator is employed for transmission in each direction and each of these-generators -is-controlled in response to signal currents: which flow from adetector of a received carriertewe T e-inp t o ea h detector is i linvention relates to signal systems and I and in whiohFigZ represents a modification 'ductively associated withthe output from the transmitter which is'employed for transmission in the opposite direction and in'consequence a complete singing circuit exists through thetwo channels thus mutuallyconnected together. If currents from; one trans-V mitter reach the opposite detector the'otheri transmitter will be causedto operate which inturn will supplycurrents to the detector associated with the first'transmitter and the above-mentioned singing will result, Such will be the case eventhoughthe amount of energy which reachesthe: two detectors is very small. Thus the protection which is applied to each channel must be very complete such as that which is afforded by a mechanical relay having contacts whichare'arraniged to open'circuit, or short circuit, or both, either'of the channels in response-to operation ofthe opposite channel;

In the useof mechanical relays difficulties areencountered"resu ting from the time deincident to'the actuation of the armatures thereof. Accordin ly oneof'the purposes of my invention is to so arrange'a mechanical relay in the'circuit such that it may be oper- "ated' in response to signalcurrents without producing undesirable 'eii cts resulting from the time delay incident to the operation of its armature,

A further purpose of my invention is to provide means whereby asignal circuit may be automaticallycontrolled by means of a 'mechanical relay in response to operation of an electron discharge device such as an amplifier or oscillation generator without detrimentally affecting the operation of those devices.

The novel features which I believe to-be characteristic of: my invention"will be set forth with particularity in the appended claims. My invention itself however; both as to its organization and method of operation, may best be understoodbyreference to the following description taken in' 'connec Fig.1 shows one form" of my invention as applied to a carrier current repeating circuit thereof,

c tion with the accompanying drawing in which 7 I Referring to Fig. l of the drawing, in which I have shown as much of the equipment as is necessary to an understanding of my invention, 1 represents the apparatus which is operated during transmission in one direction and 2 represents the apparatus coils are connected through circuit-s Sand 6' respecti 'ely to suitable antenna systems or to wire line circuit-s such, for example, as those of the usual power distribution system. These hybrid coils are also prov dedx 1n the usual manner, with balancing networks '4' and 8 respectively.

- Inthe channel 1 is employed an electron discharge oscillation generatorl), between the anode andgrid of which is connected the usual osclllatory circuit 10. High frequency currents are supplied from this oscillation generator through the coupling condenser 11; suitable amplification and modulation apparatus 12, and conductors 13 to the hybrid coil 3, from which they EI-FQCOIYllDUIllCELlZQCl to the transmission media through the circuit The oscillation generator 9 is adapted to be controlled in response to received signals by means of an electron discharge device 14. This device isof theusual three element type and has the space between its anode and cathode connected in circuit with the discharge pathof the oscillation-generator 9.

This circuit may be traced from the negative side of the source of potential '15 through conductor 16, resistance 17. space between the cathode and anode of the dischargedevice 1.4, spacebetween the ca Unode andanode of the discharge device 9 and choke coil 18 .to the positive side of the source of potential 15. Normally the impedance of the discharge device 14 is such that substantially no currentfiows in this circuit and hence theelectron discharge devicei) is normally inoperative. This impedance may be obtained by supplying suitable biasing potential to the 'd of device 14. W hen high frequency currents are received from the circuit 6 they are detected by the device 19 and the signal currents therefrom are impressed upon the grid of the control device 14. The impedance between the anode and cathode of this device is then sufficiently diminished to permit current to flow through the anode circuitof the oscillationigenerator 9, and hence this device is rendered operative. High frequency currents are then supplied by the oscllla ion generator 9 to the apparatus 12, where they are modulated by signal currents which are supplied thereto through the conductors 20. These modulated high frequency currents are then supplied to the transmission media through the hybrid coil 3 and circuit 5.

Channel 2 which is adapted for communication in the opposite direction is identical with the channel 1 and hence its circuit con 'struction will not be more fully explained.

When high frequency, currents. are received vfrom the circuit 5 they are impressed upon the grid of the detector 21 where the voice, or signal, currents are detected. These voice, or signal, currents are then supplied through the transformer 22 :0 the transmitting apparatus 23 where they are impressed upon the grid of a control device corresponding to the device l l of the channel 1 and also upon suitable modulationapparatus. High frequency currents produced by the oscillation generator, which is included in the apparatus 23, are then communicated through the hybrid coil 4 and circuit 6 to the transmission media.

As thus constructed it will be seen that,

during operative periods of'the oscillation generator 9, if currents from this device reach the detector 21 and the controldevice associated with the transmitting equipment 23,

high frequency currents will be supplied through the hybrid coil l, both to the line 6' i and to the channel 1. This is particularly true inview of the difiiculties encountered in balancing these hybrid coils to currents having the frequency of the carrier wave. These currents will then in turn cause theoperation of oscillation generator 9 which will con tinue to supply currents through the hybrid coil 3. .ihus singing of the circuit'will result.

To prevent this a. relay 2% having a pair of normallyclosed contacts 29 and 30-and a pair of normally open contactsv29 and 31 is provided, such that when this relay is energized the input to the transmitting device-28. is open circuited by the contacts 29 and 30 and the output from the detector 21 is short circuited by the contacts 29 and 31. Thus no transmission of energy through this channel can take place. Inaccordance with my invention meansare provided whereby this relay may be caused to quickly respond to the direct current flowing in the anode circuit of the oscillation generator 9.

In common with circuits in which reactance is included the current in the anode circuit of the oscillation generator 9, after voice currents have been applied to the grid of the control device 14, builds up in accordance with an exponential characteristic. After the current in thiscircuit has built up to a certain value oscillations will be produced by the device 9. To produce quick response of a pair of contacts, such as those of the relay 24C, to application of signal currents to the transmitter by means of this current it is necessary that the relay should operate before the current reaches its normal value and preferably while it is at a small fractional part of its normal value. Were the actuating coil in response to a small fraction of this current it .will be seen that-a very sensitive relay and one having high resistance would necessarily belemplfoyedi-z Unless additio'nal -i iea 'is are employed a thigh voltage will; be producedi pedance is connectedthe space betweenthe 1 grid-and. cathode ofgan electron dlscharge deacross the -relayuvhen"normall current flows In accordance with the form shown in Fig.

1 I have included in the anode circuit-0t the oscillation-generator 9 animpedance 17 as above me'ntioned;.v In parallel with this imvice 25- in the anode --circ'u it' of which I is includ'edthe relay; 24 and an additional relay 26', the purposeyotthe latter of'which 'will later. besetwforth-r A source otbiasing'potentialQT. is used to normally impress a negatiie'potentialupon the grid of the discharge throughi theiresistance 17,-='the space between the grid and cathode of the. device 7 25" representsa very large'impedance: The effect of this potential'is also to preclude the flow-of anodecu-rrent through fthedischarge device .25?and hence throughthe actuating windlngs 'otthe relays 2 L: and-26L W hen currentis caused to flow-in theresistance l7,however,

as due to signal-currentsbeing appliedto the grid: of the device Y '14- this biasing potential will be overcomezand currentwill be caused tofiow thrcughtherelays- 24- and 26 having sufiicient magnitude to cause the operatlon. o-I" the'rlevice 2% whenthe anode current of the oscillation generator 9 is still at av'ery small value. As this current increases the impedance between the grid and cathode ofithe device 25 is diminished and'hence when the anodecurrentot-the device 9 reaches its nor- :mal talue 'a very substantial portion thereof,v

which .may be {50% or greater will flow through the space between thefcathodel-and grid of the device 25"rather than through the resistance 17; Thus after the device 24: is

- operated the 1 impedance across the terminals oi t-he resistance 17 is increasingly diminished and hence-the potential appearing across the resistance -17 'dOGSIIlOlJ become-of magnitudesuch that it impairs the operation of the oscillation generator 9. In this manner a very rapid response of the relay 2d can be produced in response to application of the signal currentsto the transmitting circuit- In fact it has been found that the relay 24 can be caused to operate before the initiation of high frequencycurrents by the generator 9. i a

The oscillation generator 9 is provided with the usual grid leak resistance 28.

cuite'd' by means of they contacts ofrelay "26. Relay 26-is sow-adjusted that its contacts do not separate until the: current in the anode circuit of ;the, oscillation generator 9 has built up to a certain desired value way operation of. the. oscillation generator 9 In this;

in responseto noises-which may normally eX- ist: in'thez operating room may be prevented. In-alnannerqsinnlar to that above described -when currentsare received from the line:5 and are detected by the device 21; and suppliedlto the} transmitter equipment 23,

protection-will heap-plied tov the channel 1 r throughficonductors 32 which lead toa relay I corresponding;totherelay: which is in cluded in the receiving apparatus 19;

Reterringto Fig; 2, Ihave shown a modification'ot my'inve'ntion in: which the relay 24; is connected directly in circuit with the cath- V ode "and anode 'ofjthe' control de ice leans OscillatiohgeneratOr 9 not shown; This rej j lay is; Of-high resistance and" is adapted to operate in response-to a smallfraction ot' the normal,anode'current. In parallel with the relay :24: is connected a. two electrode discharge; device 25 whiclris provided with a source of biasingpotential 27. I As thus ar 251. The'impedance' of this g-device willthen become greatly diminished and when the anode currentof device lat approaches its norinal value a substantial portion of it will now through {the devicea25 In; this wayvzthe .buildinggu of a large potential-upon-the relay.- 24: is: prevented.

rangedy'as; the current-through therelay 24 7 increases the relay ,will be caused toyoperate andwthe' ipot'ential appearing thereon'wwill v overcome the biasing potential ot the device rVVhileIhave describediny means for pro I ducing-za rapid response of a relay such; as

relay 2% with .iparticular reference to? signal r systems and tozits application to the control circuitswof such systemsgand also with particular reference tothe' controlhngof relay contacts in response to the anodecurrent fiowing rin anoscillation generator, it will; not course; be understood that I do-not wish to belimited theretosince mysystem maybe employed in any case where I it; is desired to operate-a relay inresponse-to current flowing '111 an operating circuit without SGZlOUSlf/fiftesting-the operation ofthe circuititself as bycausing: a large potential to appear across the relay;

Likewise while Ihave shown anddescribed a single embodiment'ot myinvention it will, ot courseybe understood that I do not wish tobeslimited thereto since ;many=-1nodificati,ons-,:,-both: in the circuit arrangement, and

in: the instrumental-ities' employed,- may be made without departing from thejspirit and scope ot 'my' invention: as settorthfin the appended claims 7 7 This 7 resistance is adapted to be normally short cir- What I claimg a-s new and desire to. secure 1 by Letters Patent otstheUnited States is 1. In combination, a circuit, a pair of contacts, means foroperating said contacts in response to current flow ng in said circuit without substantially changing the charac- 1 teristics of the circuit to normal flowof'cur- 7 rent therein, said means including an impedance'connected in said circuit and means for causing operation of said contacts in response a to the potential on said impedance when the current flowing therein is equal to'afractional part of the normalcurrent and for producing a shunt around'said impedance for currents of value greater than said fractional part,

.saidshunt having impedance suchthat under normal operat ng conditions ofsaid circuit a I substantial portion of the current in said cir- V cuit flowsthrough said shunt. r

' 2. In combination, anelectron discharge device hav ng an anodecircuit, means for controlling said anode circuit thereby to control the operation of said discharge device, a pair of contacts, an impedance connected in said a anode circuitand means for operating said contacts n response to potential on said impedance'whe'n the current flowing therein is o a fractional part of the normal-value and shunt whereby said contacts .areoperated without materially affecting thenormaljoperation of said discharge device.

8. In a signaling system, a receiving circuit,-a transmitting circuit including anormally inoperative electron discharge device having an anode circuit, means for rendering said device operative in responseito application of signal currents to said transmit- 1 ter, a pair of contacts for controlling said receiving circuit, an impedance connected in said anode circuit and means for operating said contacts in response to the potential on said impedance when the current therein is a fractional part of thenormal value and for producing a shunt around said impedance for currents greater than said fractional part.

4. Ina signaling system, a receiving circuit, a transmitting circuit including a normally inoperative electron discharge device having an anode circuit, means for rendering tion of" signal currents to said transmitter, a pair of contacts "for controlling said receiving circuit, an impedance connected in said anode circuit, means for operating said contacts in response to the potential on said, impedance when the current therein is a fractional part ofthe normal value and an elec tron discharge device connected in shunt with said impedance having highresistance for values of current in said impedance smaller than said fractional part and low resistance for Values of current tional part. a

5. In combination, an electron discharge oscillation generatorhaving an anode circuit,

a relay,5means for operating'said relay in greaterthan said fracvresponse to rise in current in said anode circuit, said means comprisingan impedance connected in said anode circuit, an electron discharge dev ce having grid and anode circuits, said relay being connected in said last connected insaid anode circuit, an electron.

discharge-device having grid and anode cir-- cuits, said relay being connected in said last "anode circuit and said impedance being included in said grid circuitwher'eby when the current in saidimp edance rises said relay is caused to operate and the impedance of said device is reduced sufficiently to permit a substantial portion of said anode current to flow through said grid circuit and additional means responsive to said rise in current for controlling said oscillation generator.

17. In a signal system, a receiving circuit, a transmitting circuit including. an electron discharge oscillation generator having an anode" circuit, means for controlling said, oscillation generator, means for controlling said receiving circuit in response to operation of said oscillation generator, said means comprising a resistance connected insaid' anode circuit, an electron discharge device having "an anode, a cathode and a grid, said cathode and grid being connected in shunt with said resistance, means for biasing the grid of said device such'that the impedance between said gridand cathode is high .when no current flows insaid resistance and becomes comparatively low when the current in said resistance approaches normal value, and a relay connected between said anode and cathode V a for controlling said receiving circuit. said device operative in response to applica- In witness whereof, I have hereunto set my hand this 16th day of March, 1928.-v

WILLIAM A. TOLSON. 

